Diabetes is a chronic life threatening disease for which there is presently no cure. It is the fourth leading cause of death by disease in the United States and over a hundred million people worldwide are estimated to be diabetic. Diabetes is a disease in which the body does not properly produce or respond to insulin. The high glucose concentrations that can result from this affliction can cause severe damage to vital organs, such as the heart, eyes and kidneys.
Type I diabetes (juvenile diabetes or insulin-dependent diabetes mellitus) is the most severe form of the disease, comprising approximately 10% of the diabetes cases in the United States. Type I diabetics must receive daily injections of insulin in order to sustain life. Type II diabetes, (adult onset diabetes or non-insulin dependent diabetes mellitus) comprises the other 90% of the diabetes cases. Type II diabetes is often manageable with dietary modifications and physical exercise, but may still require treatment with insulin or other medications. Because the management of glucose to near-normal levels can prevent the onset and the progression of complications of diabetes, persons afflicted with either form of the disease are instructed to monitor their blood glucose concentration in order to assure that the appropriate level is achieved and maintained.
Traditional methods of monitoring the blood glucose concentration of an individual require that a blood sample be taken daily. This invasive method can be painful, inconvenient, and expensive, pose the risk of infection and does not afford continuous monitoring. So-called semi-invasive (or less-invasive) methods require an individual to take samples through the skin but the techniques do not puncture blood vessels. Most semi-invasive glucose monitoring devices measure the concentration of glucose that is present in the interstellar fluid that is between the skin's surface and underlying blood vessels. The devices could be implanted to provide continuous (real time) glucose level monitoring but individuals would have to undergo implantation surgery. Moreover, once implanted the devices are often inaccessible for maintenance.
Another glucose measuring method involves urine analysis, which, aside from being inconvenient, may not reflect the current status of the patient's blood glucose because glucose appears in the urine only after a significant period of elevated levels of blood glucose. An additional inconvenience of these traditional methods is that they require testing supplies such as collection receptacles, syringes, glucose measuring devices and test kits. Although disposable supplies have been developed, they are costly and can require special methods for disposal.
Many attempts have been made to develop a painless, non-invasive external device to monitor glucose concentrations. The various approaches have included electrochemical and spectroscopic technologies, such as near-infrared spectroscopy and Raman spectroscopy. These systems measure blood glucose concentration based on IR blood absorption and emission at selected wavelengths. A major problem with these non-invasive optical techniques is that blood glucose absorption in the near, mid or far IR regions is very weak. Compounding this problem is the fact that water, proteins, fat, and other tissue components tend to blur the glucose fingerprint and thereby attenuate the detectable signals and as a result these blood glucose monitoring devices are not very accurate. Techniques used to compensate for the poor signals and the related signal-to-noise problems including complicated spectral analysis and processing instrumentation have not been successful. Thus, despite extensive efforts, none of these methods has, so far, yielded a non-invasive device or method for the in vivo measurement of glucose that is sufficiently accurate, reliable, convenient and cost-effective for routine use.